The technical field of this invention is catheter-based methods and devices for treatment of cardiovascular conditions.
Diseased sites in blood vessels, such as atherosclerotic plaques, aneurysms, stenotic lesions, blocked arteries, and the like, have often been treated using catheters that deliver light, heat or therapeutic agents to the treatment site. Catheters used for this purpose are designed to fit suitably into the lumen of the vessel under treatment.
In U.S. Pat. No. 5,053,033 issued to Clarke, UV radiation is delivered by means of an optical fiber incorporated in a catheter to reduce incidences of restenosis at an angioplasty site. The blood vessel walls are irradiated with UV light during the course of angioplasty procedure, and the effect of the irradiation is to reduce proliferation of smooth muscle cells at this site.
In U.S. Pat. No. Reissue 34,544 issued to Spears et al., therapies are disclosed based on the administration of haematoporphyrin, which is selectively taken up by atherosclerotic plaques. Subsequently, light in the IR range is delivered to the plaque, resulting in the lysis of the plaque. A balloon catheter equipped with a flexible optical fiber is used to deliver the light. When the balloon is inflated, it displaces the opaque blood, allowing transmission of the IR energy through the balloon to the plaque.
In U.S. Pat. No. 5,620,438 issued to Amplatz et al., a balloon catheter is disclosed that causes the radiant energy to exit the catheter in a radial band to treat blood vessel walls. The area of the vessel wall is exposed to the radiant energy in a controlled manner following balloon angioplasty to reduce the tendency of restenosis.
In U.S. Pat. No. 5,797,868 issued to Leone, a photodynamic balloon catheter is used to evenly distribute radiation to the vessel wall. The catheter has a light passing inner tube, a light passing fluid and a light passing inflatable balloon. Light emanating from an optical fiber is reflected through these components to provide uniform illumination within the blood vessels.
Medicaments can also be administered to a subject using catheters. The advantage of using a catheter is that the catheter provides a direct delivery of the medicament to the target site. This minimizes the chance of side effects often encountered by systemic administration of the medicament. In U.S. Pat. No. 5,087,244, issued to Wolinsky et al., a catheter with a flexible balloon having a plurality of minute openings is used to deliver drugs to the vessel. For example, the balloon can be inflated with a heparin solution, and as the walls of the balloon contact the arterial wall, the heparin exits the balloon, directly onto the walls.
However, a serious drawback to using catheters for these types of treatments is that the catheter blocks the flow of blood through the vessel distal to the delivery site, depriving tissue of needed blood. This can cause tissue damage, even when the procedure is performed expediently. Therefore, the amount of time available for drug or light delivery is limited.
The object of this invention is to provide a catheter that can deliver light, heat or a therapeutic agent to a target region in a vessel wall without occluding blood flow in the vessel.